The invention relates to an apparatus for performing at least two measurements of characteristics in a particle suspension.
Such apparatuses are known, for example, from U.S. Pat. No. 3,710,933; and the article by Steinkamp et al., in Rev. Sci. Instrum., Volume 44, No. 9, September 1973, pages 1301-1310, cf. particularly FIG. 2 on page 1302.
What is involved is a combination of a measurement in accordance with the Coulter principle involving a fluorescence measurement with the aid of an optical device, the filamentary particle stream being upstream of a measuring aperture in which the volume is measured, and conducted past observation windows, through an exciting radiation, e.g., a laser radiation is radiated onto the particles, with the fluorescence induced in the course thereof being measured; at the same place the measurement of the light scattering may also be made. Thus, two parameters, viz. the volume and the fluorescence, are measured at two measuring locations arranged one behind the other. For the purpose of the evaluation, it is important to coordinate the results of the measurement of one parameter with the results of the measurement of the other parameter. In the evaluation of the measuring results measured at the two measuring locations, account must be taken of the time of the passage of the particles between the two measuring locations (cf. in this connection U.S. Pat. No. 3,710,933, column 10, lines 31-34). This involves a grave disadvantage; the time of passage, which has to be accurately adjusted, depends particularly on a variety of influencing parameters, e.g., velocity of flow of the medium, temperature, pressure differentials, etc., all of which are sources of possible measuring errors.